pc/g3doc/sctp_transport.md

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# SctpTransport

## webrtc::SctpTransport

The [`webrtc::SctpTransport`](https://source.chromium.org/chromium/chromium/src/+/main:third_party/webrtc/pc/sctp_transport.h;l=33?q=class%20webrtc::SctpTransport) class encapsulates an SCTP association, and exposes a
few properties of this association to the WebRTC user (such as Chrome).

The SctpTransport is used to support Datachannels, as described in the [WebRTC
specification for the Peer-to-peer Data
API](https://w3c.github.io/webrtc-pc/#peer-to-peer-data-api).

The public interface ([`webrtc::SctpTransportInterface`](https://source.chromium.org/chromium/chromium/src/+/main:third_party/webrtc/api/sctp_transport_interface.h?q=webrtc::SctpTransportInterface)) exposes an observer
interface where the user can define a callback to be called whenever the state
of an SctpTransport changes; this callback is called on the network thread (as
set during PeerConnectionFactory initialization).

The implementation of this object lives in pc/sctp_transport.{h,cc}, and is
basically a wrapper around a `cricket::SctpTransportInternal`, hiding its
implementation details and APIs that shoudldn't be accessed from the user.

The `webrtc::SctpTransport` is a ref counted object; it should be regarded
as owned by the PeerConnection, and will be closed when the PeerConnection
closes, but the object itself may survive longer than the PeerConnection.

## cricket::SctpTransportInternal

[`cricket::SctpTransportInternal`](https://source.chromium.org/chromium/chromium/src/+/main:third_party/webrtc/media/sctp/sctp_transport_internal.h?q=cricket::SctpTransportInternal) owns two objects: The SCTP association object (currently
implemented by wrapping the usrsctp library) and the DTLS transport, which is
the object used to send and receive messages as emitted from or consumed by the
usrsctp library.

It communicates state changes and events using sigslot.

See header files for details.